Patients undergoing oral surgery will typically be prescribed by their doctor to have a medical scan record created of the affected cranio-facial region of the respective patient's skull. Such medical scan records can include computerized axial tomography (CT scan or CAT scan) records, Cone Beam Computed Tomography (CBCT) records, and Magnetic Resonance Imaging (MRI) records. For example, patients undergoing correction of facial deformities, facial reconstruction after injury, and placement of dental implants often will have such a CAT scan, CBCT scan, or MRI scan performed prior to treatment or surgery.
CAT scan records can essentially be described as a series of X-Rays taken a short distance apart along a set path, whereby a three-dimensional presentation of the patient's bone structure, nerves, and facial soft tissue can be generated on a computer screen for aiding the doctor in the determination of the patient's treatment diagnosis. CBCT scanners use a cone shaped x-ray beam to generate a volume of data that can be reconstructed to produce a stack of two-dimensional gray scale level images. Cone beam tomography scanners emit lower radiation than traditional dental x-rays. MRI scanners produce a rotating magnetic field within the body that is detectable by the scanner. For the purposes of this document, the terms CAT scan, CBCT scan, and MRI scan will be referred to collectively as 3D medical scans.
In the application of oral surgery, 3D medical scan records commonly have missing or inaccurate medical information in the region of the teeth occlusal surfaces. Some missing or inaccurate data is caused by the presence of metal dental fillings or metal dental prostheses (crowns, bridges, etc.) in and/or near the patient's teeth. Metal tends to scatter the gamma X-rays generated during the scans, thereby producing a “data void” in the oral region of the scan record in which the metal is present. 3D medical scan accuracy also can be limited by voxel size. In the case of CT scans, imaging accuracy can be limited by the amount of radiation the patient can tolerate in each scanning session. For years, efforts have been made to improve 3D medical scanning accuracy. To date, however, the problem of missing and/or inaccurate medical information in the regions of the occlusal surfaces has not been eliminated.
More accurate electronic data records of teeth occlusal surfaces (hereafter referred to as “dental models”) can be generated by scanning the teeth directly, by scanning impressions of the teeth, and/or by scanning models (e.g., casts) of the teeth using a laser-line scanner, optical scanner, or touch scanner. For example, U.S. Pat. No. 6,217,334 (Dental Scanning Method and Apparatus) and U.S. Pat. No. 6,579,095 (Mating Parts Scanning and Registration), each of which are commonly owned by the assignee hereof, disclose systems for creating one or more electronic, three-dimensional, laser-imaged, dental models of patient teeth and surrounding soft tissues (hereafter referred to collectively as “dentition” for convenience). These two identified patents are hereby incorporated herein by reference and made a part hereof.
Efforts to physically locate such dental models into 3D medical scan records have generally required the use of artificial fiducial structures or markers. More specifically, several markers are typically arranged on a dental impression tray, which is held in the patient's mouth during acquisition of the 3D medical scan record. The teeth are then scanned intraorally with the markers arranged in the same position to obtain one or more dental model records. Alternatively, an impression tray or a study cast can be digitized (e.g., through laser scanning, touch-probe scanning, optical scanning, etc.) subsequent to the 3D medical scan to create one or more dental models (e.g., polygonal mesh models) of the teeth. The markers function as fiducial or registration points when combining the dental model record and the 3D medical scan record.
A drawback of these previous efforts, however, is that the 3D medical scan records and the dental models cannot be taken concurrently. Further, it can be beneficial to combine the 3D medical scan records and the dental model records even when the records were not initially taken with the intention to combine the same (e.g., when the records were taken without artificial fiducial structures).
Therefore, there arises a need for a method and apparatus which provides for combining dental model records with 3D medical scans and/or enhances the 3D medical scan medical records of patients considering or undergoing oral surgery.